/kubernetes-essentials

Kubernetes Basics

important components

On Master

  • API Server : Main communication hub, rest API service.
  • Scheduler: Responsible for assigning worker nodes.
  • Controller : Backend for API server.
  • etcd: data store that stores the cluster configuration.

On Nodes

  • kublet: Runs and manages pods and talks to API server.
  • kube-proxy: load balancing traffic between components.
  • container runtime: program which runs containers/ responsible for communicating to container provider. (eg. docker etc)

Installing Kubernets: Click

Simple nginx pod:

cat << EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - name: nginx
    image: nginx
EOF

View pod:

This pod will be created in default namespace hence,

kubectl get pods

API Primetives:

Required fields:

  • apiVersion - Which version of the Kubernetes API you’re using to create this object.

  • kind - What kind of object you want to create.

  • metadata - Data that helps uniquely identify the object, including a name string, UID, and optional namespace.

  • spec - What state you desire for the object.

Compponent status
kubectl get componentstatus

Create deployment from yaml. nginx-deployment.yaml

kubectl create -f nginx-deployment.yaml

get full yaml back

kubectl get deployments nginx-deployment -o yaml

Show all pod labels.

kubectl get pods --show-labels

adding label to the pod

kubectl label pod <pod-name> env=prod

find pod with label

kubectl get pods -L env=prod

view specific label of all pods

kubectl get pods -L env

Use field selector

kubectl get pods --field-selector status.phase=Running

Some important command reference

view Kubernetes cluster information

ubectl cluster-info

view Kubernetes kubeconfig settings

kubectl config view

Show all node details

kubectl describe nodes

Show all pods details

kubectl describe pods

show all service details in all namespaces

kubectl get services -all-namespaces

View all resources

kubectl api-resources -o wide

Validating kubernetes cluster

Run simple nginx deployment

kubectl run nginx --image=nginx

view deployments

kubectl get deployments

view pors

kubectl get pods

Port forward test

kubectl port-forward <pod name> 8081:80

From same host can check result on port 8081 curl localhost:8081

View logs

kubectl logs <pod name>

Running command inside the pod

kubectl exec -it <pod name> -- nginx -v

Create service using deployment

kubectl expose deployment nginx --port 80 --type NodePort

View all services

kubectl get svc

Get detaied information about nodes

kubectl describe nodes

Get detaied information about pods

kubectl describe pods